A plurality of products made from particles or beads of expanded plastic materials are widely employed, for example as heat insulating materials, packaging materials, cushioning materials, or energy absorbers.
Energy absorbing elements are used in particular in the structure of motor vehicles in order to receive a large part of the kinetic energy of impact, and thus to increase the safety of occupants and pedestrians. Prior art applications are shock absorbers, side doors, and impact deflector elements which are used for the support of bumpers with respect to the supporting body structure.
Over the past few decades, energy absorption management has become an increasingly important part of the design and construction of modern transportation vehicles. Early on, it was recognized that vehicles designed with deformable front and/or rear structures provided greater safety to vehicle occupants in the case of a crash, due to the impact energy absorption by the structure as it deforms. It has become increasingly common to design vehicles, particularly automobiles, in this manner. However, while deformable structures such as these are helpful in preventing or minimizing injuries to passengers, as a result of the severe structural damage done to the vehicle, repair and reconstruction of the vehicle is an expensive and time-consuming practice. Repair procedures are especially viewed as unnecessary when the impact involves low to moderate energy, which might be encountered in bumper-to-bumper contact in a parking lot, for example. To mitigate against damage caused by such relatively energy deficient impacts, it has become common to mount automobile bumpers by resilient but energy absorptive mounts, or to prepare the bumpers themselves out of energy-absorptive material. For example, expanded polypropylene (EPP) within a glass fiber reinforced exterior shell has been used for such purposes, the EPP providing for excellent energy absorption coupled with resilience enabling the bumper to spring back to its pre-impact shape, and the glass fiber reinforced shell providing sufficient structural strength for the bumper to serve as a structural as well as energy-absorptive component.
Concerns with vehicular impacts have extended to the passenger compartment as well, and over the past few decades, the plethora of angular objects extending into the passenger compartment such as window cranks, door handles, door lock buttons, and the like, have decreased, have been recessed so as to no longer protrude, or been eliminated entirely. Moreover, many of the car interior materials such as those found in dashboards, side bolsters, pillars, and even seats and headrests, have been selected with impact energy absorption in mind.
Current processes for making expanded plastic materials involve placing a mold inside a steam chest, filling the mold with plastic pellets and filling the steam chest with steam such that the steam enters the mold through vents in the mold, allowing the pellets to expand and fuse together. Thus, in a steam chest, the mold components are exposed to an immoderate environment of extreme temperatures and humidity. In order to mold products with out of die draw features in such a steam chest, the mold requires additional members aside from the mold core and cavity. Providing fixed members, such as fixed pins for forming holes, would cause a locking condition resulting in a damaged part upon ejection of the molded products. Furthermore, any devices used to retract such pins, such as hydraulic cylinders, need to be enclosed or sealed within the steam chest. However, difficulties arise when providing retractable mold members inside the steam chest because of the immoderate conditions therein which can lead to mechanism failures.
Thus, it is desirable to provide products molded in a steam chest that have out of die draw features.
It is furthermore desirable to provide an apparatus for molding products in a steam chest that provides for the molding of out of die draw features.
It is further desirable to provide a method for molding plastic products in a steam chest having out of die draw features.